1. Field of the Invention
This invention relates to an actuator for driving a work holding chuck into clamping position to hold a tubular workpiece in a machine tool or the like.
2. Related Information and General Discussion
It is common to use various arrangements of chucks to hold workpieces, particularly tubular workpieces, in clamped position in machine tools designed to perform machining or cutting operations on the workpiece. When split collet chucks are used with tapered bearing surfaces or the like, relative axial movement of the collet sections and their bearing surfaces drives the collet sections radially inwardly, or outwardly, depending on the design of the chuck, to clamp onto the adjacent periphery or circumference of a tubular workpiece extending axially through a center bore of the collet or about the periphery of the collet sections. Such collets may be regarded as axially actuated in the sense that they are driven into engagement with a workpiece in response to relative axial movement between the collet sections and their bearing surfaces.
In such axially actuated collet type chucks, some means must be provided to apply axial motion to the collet system to effect clamping of the workpiece. It is common to use rotary threaded thimbles, levers, thrust nut elements and the like that are mechanically or manually moved to apply axial thrust against the collet systems for clamping workpieces in the collet. Such collet arrangements can be seen, for example, in U.S. Pat. Nos. 489,933--Conradson; 658,473--Smith et al.; 123,197--Plinton et al.; 425,224--Hartness; 1,400,306--Miller; 2,460,149--Schoensiegel; 2,517,346--Queitzsch; 2,735,689--Madsen; and 4,319,503--Saine et al.
It is highly desirable that split collet work holders be actuated by quick setting and release arrangements that permit rapid securing and release of workpieces in a tool to enable high rates of productivity with the tool. Several of the prior art patents mentioned above include such quick setting and release mechanisms. However, they generally lack simplicity, low cost, and the ability to quickly change the collets to accommodate different size workpieces. Also, the various prior art collet actuators require somewhat complicated and relatively heavy structural arrangements that maintain the collet driving mechanism parallel to the collet system so that all collet sections are driven into clamping position uniformly so that the workpiece is maintained centered in the central bore of the collet.